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Life cycle analysis using Argonne GREET model of algae based biofuels produced utilizing flash hydrolysis process
Andrew P. Bessette
Dr. Sandeep Kumar
Civil and Environmental Engineering
Abstract
Traditional processing methods of algae to biofuels require
dewatering after harvesting of the algae before the lipids
can be extracted. This is typically the most energy
intensive and therefore the most expensive step. Old
Dominion University has successfully utilized a flash
hydrolysis process where proteins are solubilized into the
liquid phase of product and the remainder lipid-rich, low
nitrogen product is separated into a solid phase. The
GREET model was used to quantify the LCA from WTW
production of biodiesel, renewable gasoline, and
renewable diesel II utilizing the flash hydrolysis process.
Results were compared with existing model simulations
from their algae Harmonization study and algae HTL study
and also with existing conventional petroleum based
reformulated gasoline (RFG) and conventional petroleum
based low-sulfur diesel (LSD) LCA’s.
Introduction
References
• Argonne National Laboratory has developed the Algae
Process Description (APD) to be used in conjunction with
the Greenhouse Gases, Regulated Emissions, and
Energy Use in Transportation (GREET) modeling system.
• Covers all 5 life cycle stages:
1. Feedstock cultivation,
2. Feedstock transport,
3. Biofuel production,
4. Biofuel transport, and
5. Biofuel end use in vehicles.
• Feedstock cultivation and biofuel production have key
stages which interact through the APD:
1. Nutrient consumption and recycling,
2. biomass harvesting and drying
3. Oil extraction
4. Conversion of oil to fuel
• GREET outputs include total energy use, fossil fuels,
natural gas use, coal use, petroleum use and carbon
dioxide equivalent green house gases (GHG’s).
• Two existing and published models for well-to-wheels
algae biofuel production exist, the harmonization study
and the hydrothermal liquefaction study (HTL).
• The complete life cycle analysis (LCA) was completed in
accordance with ISO 14040:2006 and ISO 14044:2006.
• Functional unit based on 1 mmBtu of fuel production
• Comparisons include:
• ODU algae process biodiesel vs. harmonization
biodiesel vs. HTL biodiesel vs. petroleum diesel
• ODU algae process renewable diesel II vs.
harmonization renewable diesel II vs. HTL
renewable diesel II vs. petroleum diesel
• ODU algae process renewable gasoline vs.
harmonization renewable gasoline vs. HTL
renewable gasoline vs. petroleum gasoline
1. Garcia-Moscoso, J.L., et al., Flash hydrolysis of
microalgae (Scenedesmus sp.) for protein extraction and
production of biofuels intermediates. The Journal of
Supercritical Fluids, 2013. 82(0): p. 183-190.
2. ISO 14040:2006, the International Standard of the
International Standardization Organization, Environmental
management. Life cycle assessment. Principles and
framework.
3. Frank, E.D., et al., 2011, User Manual for Algae Life-Cycle
Analysis with GREET: Version 0.0, Draft, Argonne
National Laboratory, Argonne, Ill.
Results
Methods & Materials Conclusions
• All algae oil extraction techniques used in the
simulations present in this study produce cleaner and
greener transportation fuel.
• The biodiesel simulation was closest to achieving total
energy consumption equal to its conventional fuel
counterpart. This is due to the biodiesel blend only
consisting of 20% biofuel. The total energy btu/mmbtu
values were 112% for HTL, 133% for the ODU flash
hydrolysis, and 138% for the harmonization study
when compared to conventional diesel.
• The renewable diesel II simulation had total energy
btu/mmbtu values of 147% for HTL, 258% for the ODU
flash hydrolysis, and 286% for the harmonization study
when compared to conventional diesel.
• The renewable gasoline simulation had total energy
btu/mmbtu values of 147% for HTL, 251% for the ODU
flash hydrolysis, and 280% for the harmonization study
when compared to conventional diesel.
• The energy recovery in the flash hydrolysis process
when cooling the subcritical water from 280 ̊ C to 99 ̊C
saves close to 26 MJ per hour. Additional energy
savings may be able to be gained by preheating
incoming flash hydrolysis water with the 99 ̊C water
through a heat exchanger.
• The liquid phase of the flash hydrolysis process was
not evaluated as a coproduct. This is 70% of the
reactor product and is rich in proteins and nutrients.
Future evaluation of this product in terms of market
value may allow for offsetting of costs within the algae
processing life cycle.
• Local algae cultivation may be more efficient
depending on local growing conditions.
Acknowledgements • ODU Civil and Environmental Engineering Department
• Argonne National Laboratory
Renewable Gasoline Renewable Diesel Biodiesel (20%)
Flash Hydrolyser280 ̊C, 3000 psi, τ=12 sec
=1.126 MJ/kg*31.20 kg = 35.14 MJ
= 1.8 kJ/kg* ̊K *16.80kg*255 ̊K = 7.71 MJ
=35.14 MJ + 7.71 MJ = 42.85 MJ
)* = 16.80 kg * 0.70 * 19.42 MJ/kg=228.38 MJ
)* =16.80 kg * 0.30 * 31.95 MJ/kg=161.05 MJ
=42.85 MJ + 228.38 MJ + 161.05 MJ= 389.43 MJ
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